The Glock 36 is touted by Glock as part of their SLIMLINE™ line of guns, and it's definitely slimmer than many. Slide width averages just a smidge over one inch (1.003" or so), as compared with slide widths of 0.91" for a 1911 and 1.02" for the Ruger P345. When it comes to overall width, the 1911 comes in at 1.30" and the P345 at 1.24" while the Glock 36 is just 1.11".
Glock beats these other 45s in overall width by keeping protrusions to a minimum; the only things that stick out at all are the slide release, the magazine release, and (when loaded) the extractor/loaded chamber indicator (more on that later). These items only stick out a little bit, and the only one that should be shortened is the magazine release, which could be inadvertently mashed if carrying IWB without a holster.
On the left side of this pistol's slide, we find the large "G-lock" logo, followed by "36," "Austria," and ".45 Auto." The G-lock ("lock" inside of a giant "G") is also molded into the left side of the grip portion of the frame. The rectangular vertically-grooved part you see in the frame to the rear of the trigger is the magazine release.